Method and system for improving fuel economy and environmental impact operating a 2-stroke engine

ABSTRACT

A method and system to reduce fuel consumption and environmental impact in a two-stroke engine. Fresh system oil having a TBN less than 10 is provided and used in the two-stroke engine to produce partially used system oil. The partially used system oil is withdrawn from the two stroke engine and at least one friction modifier is added to at least some of the withdrawn partially used system oil, wherein the addition of the at least one friction modifier reduces the friction coefficient of the withdrawn system oil, resulting in a system oil having reduced friction. The system oil with reduced friction is combined with partially used system oil remaining in said two-stroke and the combined system oil is used to lubricate pistons of said two-stroke engine.

FIELD OF THE INVENTION

The invention relates to a method of reducing fuel consumption,lubricant complexity and environmental impact in the operation of atwo-stroke engine. Further, the invention relates to a system forreducing fuel consumption, extended lubricant utilization andenvironmental impact in a two-stroke engine.

BACKGROUND OF THE INVENTION

Two-stroke cross-head engines used in marine and/or stationaryapplications are equipped with two separate lubricating oil systems. Onelubricating system comprises so-called system oil that normally is usedfor lubrication and cooling of the engine's bearings and e.g. oil-cooledpistons as well as for activation and/or control of various valves orthe like. The other lubricating system comprises an all-loss lubricant(cylinder oil) that normally is used for lubrication of the engine'scylinders, piston rings and piston skirt.

In typical two-stroke cross-head engines, the cylinder oil is spentcontinuously by each turn of the engine whereas the system oil inprinciple is not spent (except by smaller unintentional leakages). Thelubrication system comprising the cylinder oil is also often referred toas an “all-loss” lubrication system as the oil is spent. The use of andvarious types of both system oil(s) and cylinder oil(s) is very wellknown in the art.

The cylinder oil typically contains certain additives that function toreduce, minimize or neutralise the acid level of the cylinder system.

Typical cylinder oils usually have an SAE (Society of AutomotiveEngineering) viscosity equivalent to about 50 and normally have a totalbase number (BN) of about 40 to 70 for the neutralisation of acidproducts produced during the combustion process. Typical system oilsusually have an SAE viscosity of about 30 with a relatively low BNcontent, typically around 5 and provide long-time performance. Theseexemplary values may vary dependent on the actual application and thespecific design of the systems that the oils are used in.

In recent two-stroke cross-head engine designs involving electronicand/or hydraulic control and/or activation of valves, etc., the minimumperformance requirements of the system oil has been substantiallyincreased compared to earlier design using traditional mechanicalcontrol/activation.

The performance level of lubricants is typically measured periodicallyand may not go beyond certain limits if the oiled component's conditionshould not be jeopardized. One cause of performance loss is caused byparticle contamination. These particles include combustion by-productsand wear components, which can be partially removed by oil separators.However, in the case of two-stroke cross-head engines, one of thesources of contamination is spent cylinder oil leakage past the stuffingbox causing both the viscosity and base number of the system oil toincrease over time, a process that cannot be reversed by separators.This causes the system oil to gradually degrade over time so componentwear increases and engine efficiency decreases. When the system oil isapproaching its condemning limit it will have to be replenished orchanged.

Patent specification U.S. Pat. No. 6,074,995 discloses a frictionmodifier composition comprising an oil of lubricating viscosity andcontaining a friction-reducing amount of an additive.

Patent specification U.S. Pat. No. 5,282,990 discloses adding asynergistic blend of friction modifiers to a crankcase lubricating oilof an internal combustion engine in order to improve the fuel economy.However, there is no suggestion of how to apply this with respect to atwo-stroke diesel engines.

Patent specification EP 0 573 231 discloses triglycerides as frictionmodifiers added to oil for improved fuel economy in an internalcombustion engine.

Patent application US 2003/0171223 discloses lubricating oilcompositions with improved friction properties.

OBJECT AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method and acorresponding system of reducing fuel consumption and environmentalimpact operating a two-stroke engine that solves the above-mentioned(and other) shortcomings of prior art. A further object is to providethis in an easy and efficient way.

A further object of the present invention is to enable improvement offuel economy or fuel efficiency in a two-stroke diesel engine.

Another object is to reduce emissions from a two-stroke diesel engine.

Another object is to enable use of a less-complex consumable system oilyet providing the same performance levels as experienced withconventionally-formulated system oils.

Yet another object is to enable extended component life of a two-strokediesel engine.

An additional object is to provide a more environmentally friendlyoperation of the engine.

These objects, among others, are achieved by a method (and acorresponding system) of reducing fuel consumption in a two-strokeengine comprising the steps of: obtaining system oil/consumable systemoil from an engine, adding at least one friction modifier to at least apart of the obtained system oil, where the addition of the at least onefriction modifier reduces the friction coefficient of the obtained oil,resulting in a system oil/consumable system oil with reduced friction,and supplying said oil with reduced friction to said engine.

In this way, the fuel consumption of the engine is reduced, i.e.improved fuel economy is obtained, due to the presence of the addedfriction modifier(s) giving the system oil/consumable system oil fedback into the engine reduced friction characteristics.

Additionally, extended component operational time is obtained since lessfriction is present between the components of the engine(s) due to theaddition of the friction modifier(s). This results in less frequentmaintenance and savings of costs.

Further, reduced emissions from the engine(s) are obtained since lessfuel is used due to the less friction between engine components obtainedby the addition of the friction modifier(s) according to the presentinvention.

In one embodiment, at least one of the friction modifier(s) is/are anash-less friction modifier.

In one embodiment, the at least one ash-less friction modifier is basedon di-, tri- and/or tetra-esters of dimeric and/or fatty acids and/orfatty amides.

In another embodiment, the at least one ash-less friction modifier isbased on neopentylglycol, pentaerythritol, sorbitol, trimethylpropanol,glycerol and/or triethanolamine or blends thereof.

In a preferred embodiment, the at least one friction modifier is basedon one or more selected from the group of:

triglycerides (of animal and/or vegetable origin), such as rape seed,soy bean, and/or castor oil,

fatty phosphates,

fatty acid amides,

fatty epoxides,

borated fatty epoxides,

fatty amines, e.g. triethanolamine

polyol esters, e.g. of glycerol, pentaerythritol, neopentylglycol,sorbitol,

trimethylpropanol,

borated polyol esters alkoxylated fatty amines,

borated alkoxylated fatty amines,

metal salts of fatty acids,

sulfurized olefins,

fatty imidazolines, or

mixtures thereof.

In one embodiment, the least one friction modifier is added at apredetermined rate so that the concentration of the added frictionmodifier(s) has a concentration of 0.2-2.0% of said systemoil/consumable system oil with reduced friction.

In an alternative embodiment, the at least one friction modifier isadded at a predetermined rate so that the concentration of the addedfriction modifier(s) has a concentration of 0.5-1.5% of said systemoil/consumable system oil with reduced friction.

In an alternative embodiment, the method involves use of a consumablesystem oil, containing a simplified additive composition and/or areduced additive treat rate.

In one embodiment, the method is used offshore, on-site, on-board avessel, and/or in a land based plant.

In a preferred embodiment, the method further comprises the step of:tapping a predetermined first amount of the system oil/consumable systemoil providing tapped oil and replenishing the remaining systemoil/consumable system oil with a predetermined second amount offresh(er) system oil/consumable system oil, with tapping and/orreplenishing done continuously, near-continuously or intermittently.

In another preferred embodiment, the method further comprises the stepsof: creating a cylinder oil on the basis of the tapped systemoil/consumable system oil by determining at least one critical parameter(e.g. BN, viscosity, permittivity/capacitance and/or elementalcomposition) of the tapped oil, determining at least one desiredparameter (e.g. BN, viscosity, permittivity/capacitance and/or elementalcomposition) of the cylinder oil and adjusting said at least onecritical parameter (e.g. BN, viscosity, permittivity/capacitance and/orelemental composition) of the tapped system oil/consumable system oilaccordingly by blending the tapped oil with at least one BN modifyingadditive resulting in a created cylinder oil, and supplying said createdcylinder oil to cylinders or part of the cylinders of said engine.

In one embodiment, the system oil is selected from the group of: atraditional system oil comprising additives for longtime performance orformulated with an additive treat-rate providing long-time performance,and a consumable system oil without long-time performance additives orformulated with a reduced additive treat-rate not providing long-timeperformance.

The present invention also relates to a system for reducing fuelconsumption in a two-stroke engine, which corresponds to the method ofthe present invention and have the same advantages for the same reasons.

More specifically, the invention relates to a system for reducing fuelconsumption in a two-stroke engine comprising a blending unit for addingat least one friction modifier to at least a part of an obtained systemoil/consumable system oil, where the addition of the at least onefriction modifier reduces the friction coefficient of the obtainedsystem oil/consumable system oil, resulting in a system oil/consumablesystem oil with reduced friction and for supplying said systemoil/consumable system oil with reduced friction to said at least oneengine.

Advantageous embodiments of the system according to the presentinvention are defined in the sub-claims and described in detail in thefollowing. The embodiments of the system correspond to the embodimentsof the method and have the same advantages for the same reasons.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from andelucidated with reference to the illustrative embodiments shown in thedrawing, in which:

FIG. 1 shows a schematic block diagram of one embodiment of the presentinvention;

FIGS. 2 a and 2 b illustrate the effects of the present invention duringa test.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a schematic block diagram of one embodiment of the presentinvention. Shown is a schematic representation of at least onetwo-stroke cross-head diesel engine (300). The engine comprises onelubricating system comprising so-called system oil (301) that normallyis used for lubrication and cooling of the engine's bearings and e.g.oil-cooled pistons as well as for activation and/or control of variousvalves or the like. Another lubricating system comprises an all-losslubricant or cylinder oil (302) that normally is used for lubrication ofthe engine's cylinders, piston rings and piston skirt.

The engine (300) corresponds to well-known prior art two-stroke enginesexcept as explained in the following.

Also illustrated is, according to the present invention, a frictionmodifying method/system (100) reducing fuel consumption in a two-strokeengine. The friction modifying method/system (100) obtains system oil(301′) from at least one engine (300) where a controller or blendingunit (102) adds at least one friction modifier (101) to (at least a partof) the obtained oil (301′). The addition of the at least one frictionmodifier (101) reduces the friction coefficient of the obtained systemoil/consumable system oil (301′), resulting in a system oil with reducedfriction (301″), which is supplied back to the engine(s) (300) as systemoil.

This results in avoiding or minimising frictional losses caused bycontamination of the system oil/consumable system oil, which normallytakes place as the oil is used and which would otherwise causesubstantial diminished efficiency, increased fuel consumption andincreased emissions. Great economical savings are achieved by avoidingthis.

The system oil is preferably selected from the group of: a traditionalsystem oil comprising additives for long-time performance or formulatedwith an additive treat-rate providing long-time performance, and aconsumable system oil without long-time performance additives orformulated with a reduced additive treat-rate not providing long-timeperformance.

Preferably, the friction modifier(s) (101) is/are ash-less frictionmodifier(s), which may be based on di-, tri- and/or tetra-esters ofdimeric and/or fatty acids and/or fatty amides.

The ash-less friction modifier(s) may also be based on neopentylglycol,pentaerythritol, sorbitol, trimethylpropanol, glycerol and/ortriethanolamine or blends of two or more of the above.

In a preferred embodiment, the least one friction modifier may be basedon one or more of: triglycerides, such as castor oil, fatty phosphates,fatty acid amides, fatty epoxides, borated fatty epoxides, fatty amines,e.g. triethanolamine, polyol esters, e.g. of glycerol, pentaerythritol,neopentylglycol, sorbitol, trimethylpropanol, borated polyol estersalkoxylated fatty amines, borated alkoxylated fatty amines, metal saltsof fatty acids, sulfurized olefins, fatty imidazolines, or mixturesthereof.

The friction modifier(s) may also be other compounds, e.g. as disclosedin the cited prior art documents and elsewhere. See e.g., patentspecification U.S. Pat. No. 4,792,410 and U.S. Pat. No. 5,110,488.

According to one embodiment, the friction modifier(s) (101) is/are addedat a predetermined rate so that the concentration of the added frictionmodifier(s) (101) has a concentration of 0.2-2.0% of the systemoil/consumable system oil with reduced friction (301″). In analternative embodiment, the friction modifier(s) (101) is/are added at apredetermined rate so that the concentration of the added frictionmodifier(s) (101) has a concentration of 0.5-1.5% of the systemoil/consumable system oil with reduced friction (301″). According toanother embodiment, the controller or blending unit (102) varies therate of added friction modifier (101) according to a predeterminedscheme, i.e. so not necessarily the same rate is used all the time.

According to one embodiment, the system oil/consumable system oil is aconsumable system oil having a reduced and/or modified additivecomposition reflecting its reduced oil life.

The present invention may e.g. be used offshore, on-site, on-board avessel, and/or in a land based plant or the like.

According to a preferred embodiment of the present invention, thesystem/method further comprises a tapping and replenishing system/method(200) where a controller (202) controls tapping a predetermined amountof the obtained system oil/consumable system oil (301′) providing tappedoil (203) and replenishing the remaining system oil/consumable systemoil (301′) with a predetermined second amount of fresh(er) systemoil/consumable system oil (201). In this way, a part of the systemoil/consumable system oil to be added with a friction modifier isreplenished. Alternatively, the tapping and/or replenishing may be donecontinuously, near-continuously, intermittently or according to othersuitable schemes.

As used system oil/consumable system oil is tapped and replenished withfresh, unspent or less spent system oil, the resulting systemoil/consumable system oil is of a more consistent quality and gradualdeterioration is minimised or avoided. In this way, enhanced andconsistent performance of the initial fluids resulting in furtherreduced component wear and equipment lifecycle cost is provided.

In effect, this provides a ‘consumable’ system oil/consumable system oilas a part of the spent system oil/consumable system oil is tapped andreplenished with fresh or fresher system oil. This is novel compared toprior art system oil/consumable system oil where the systemoil/consumable system oil is kept in the engine system until about ithas been degraded too much for efficient use. After this It has to bereplaced and the spent system oil/consumable system oil would have to behandled as waste. A further advantage of this is that the requirementsfor the system oil/consumable system oil in this system are differentthan prior art requirements. Standard system oil/consumable system oilfor prior art systems usually contains an additive package to secure along lifetime of the system oil. System oil/consumable system oil with aprior art additive package is significantly more expensive than asimilar system oil/consumable system oil without the prior art additivepackage or with a new additive package designed for a “consumable”system oil. The present system can function with system oil/consumablesystem oil using a reduced and/or modified additive package ensuringsufficient oil life since it is tapped and replenished. This leads toreduced expenses since cheaper oil can be used in the system.Preferably, the tapped oil is used instead of becoming waste asdescribed in the following.

The tapping/replenishment system (200) may feed directly into the engineor be part of a separate loop, instead of the one used for addition offriction modifier(s) to the system oil/consumable system oil (301′).

In another preferred embodiment, the system/method further comprises aBN modifying system/method (400) that converts used systemoil/consumable system oil into useable cylinder oil. See e.g., patentspecifications U.S. Provisional 60/612,899 and European patentapplication number 04388064.0, both of the same applicant and bothincorporated herein by reference, for specific details of oneimplementation of a BN modifying system/method (400).

In this embodiment the BN (total base number) modifying system/method(400) comprises a controller (402) for creating a cylinder oil on thebasis of the tapped system oil/consumable system oil (203) bydetermining the BN of the tapped oil (203), determining a desired BN ofthe cylinder oil (302) and adjusting the BN of the tapped oil (203)accordingly by blending the tapped oil (203) with at least one BNmodifying additive (401) resulting in a cylinder oil (302′), where saidcylinder oil (302′) is supplied to cylinders or part of the cylinders ofsaid engine (300).

In this way, a method and system for converting/re-cycling a(used/spent) system oil/consumable system oil into a useable cylinderoil by adjusting BN is provided. This results in significant economicalbenefits since system oil/consumable system oil that otherwiseultimately would have to be disposed-of can be re-used/re-cycled as atotal-loss cylinder lubricant. In addition, a more cost-effectiveconsumable system oil can be used. Furthermore, cylinder oil does nothave to be purchased. The system oil/consumable system oil used to blendthe cylinder oil is of more consistent quality as it is replenished(contrary to the traditional practice) which reduces machinery wear,etc. Thus, the replenishment of the initial fluid(s) provides enhancedand consistent performance of the initial fluids resulting in greatlyreduced component wear and equipment lifecycle cost. Even further, amore environmentally friendly method/system is provided since waste, inthe form of spent oil(s) that is discarded after prolonged use, isreduced as it is converted into cylinder oil.

The BN modifying additive may e.g. comprise at least one base.Preferably the at least one base comprises basic salts of alkaline orearth alkaline elements, and/or detergents and/or dispersants. Thecylinder oil may be created with a BN in response to fuel oilcharacteristics and/or actual engine operating requirements. Further theBN of the cylinder oil may be chosen based upon sulphur-content of theused system oil. The used system oil/consumable system oil may e.g. beselected from a group of lubricants, hydraulic fluids, gear oils, systemoils, trunk piston engine oils, turbine oils, heavy duty diesel oils,compressor oils, etc.

The alkaline/earth alkaline elements may e.g. be K, Na, Ca, Ba, Mg orthe like. The basic salts may belong to the inorganic chemical familiesof e.g. oxides, hydroxides, carbonates, sulphates or the like. Thedetergents may belong to the organic chemical families of e.g.sulphonates, salicylates, phenates, sulfophenates, Mannich-bases and thelike. The dispersants may belong to the organic chemical families ofsuccinimides or the like.

Alternatively, the conversion of spent/used system oil/consumable systemoil into cylinder oil may be done without replenishing, i.e. the BNmodifying system (400) is connected directly into the engine or isconnected to a tapping system without replenishment.

FIGS. 2 a and 2 b illustrate the effects of the present invention duringa test. Shown in FIG. 2 a is a graph (210) illustrating the mechanicalefficiency of an engine before, during and after use of the presentinvention where system oil/consumable system oil from the engine ismodified by adding at least one friction modifier to at least a part ofthe system oil. The graph is separated into a first part (211)illustrating measurements in a period before application of the presentinvention, i.e. traditional efficiency, a second part (212) illustratingmeasurements in a period during application of the present invention anda third part (213) illustrating measurements in a period afterapplication of the present invention.

As can be seen by the graph (210) the overall mechanical efficiency,i.e. the rate between the effective power output from the engine seen inrelation to an indicated maximum power output from the engine, isincreased by modifying the system oil/consumable system oil by adding atleast one friction modifier according to the present invention. Morespecifically, it can be seen that the mechanical efficiency generally ishigher in the second and third part (212; 213) of the graph (210), i.e.during and after application of the present invention.

Shown in FIG. 2 b is a graph (210) illustrating the loss of power of anengine before, during and after use of the present invention. The graphis separated into a first part (211) illustrating measurements in aperiod before application of the present invention, i.e. traditionalefficiency, a second part (212) illustrating measurements in a periodduring application of the present invention and a third part (213)Illustrating measurements in a period after application of the presentInvention. As can be seen by the graph (210) the overall loss of poweris generally reduced in the second and third part (212; 213) of thegraph (210), i.e. during and after application of the present invention.

In the claims, any reference signs placed between parentheses shall notbe constructed as limiting the claim. The word “comprising” does notexclude the presence of elements or steps other than those listed in aclaim. The word “a” or “an” preceding an element does not exclude thepresence of a plurality of such elements.

1. A method of reducing fuel consumption and environmental impact in atwo-stroke engine comprising the steps of using fresh or partially usedsystem oil from at least one engine, adding at least one frictionmodifier to at least a part of the obtained fresh or partially usedsystem oil where the addition of the at least one friction modifierreduces the friction coefficient of the obtained system oil, resultingin a system oil with reduced friction, and supplying said system oilwith reduced friction to said at least one engine.
 2. A method accordingto claim 1, wherein at least one of said at least one friction modifieris an ash-less friction modifier.
 3. A method according to claim 2,wherein said at least one ash-less friction modifier is based on di-,tri- and/or tetra-esters of dimeric and/or fatty acids and/or fattyamides.
 4. A method according to claim 2, wherein said at least oneash-less friction modifier is based on neopentylglycol, pentaerythritol,sorbitol, trimethylpropanol, glycerol and/or triethanolamine or blendsthereof
 5. A method according to claim 2, wherein said at least onefriction modifier is based on one or more selected from the group of:triglycerides (of animal and/or vegetable origin), such as rape seed,soy bean, and/or castor oil, fatty phosphates, fatty acid amides, fattyepoxides, borated fatty epoxides, fatty amines, polyol esters, boratedpolyol esters alkoxylated fatty amines, borated alkoxylated fattyamines, metal salts of fatty acids, sulfurized olefins, fattyimidazolines, or mixtures thereof
 6. A method according to claim 1,wherein said at least one friction modifier is added at a predeterminedrate so that the concentration of the added friction modifier(s) has aconcentration of 0.2-2.0% of said system oil with reduced friction.
 7. Amethod according to claim 1, wherein said at least one friction modifieris added at a predetermined rate so that the concentration of the addedfriction modifier(s) has a concentration of 0.5-1.5% of said system oilwith reduced friction.
 8. A method according to claim 1, wherein themethod is used offshore, on-site, on-board a vessel, and/or in a landbased plant.
 9. A method according to claim 1, wherein the methodfurther comprises the step of: tapping a predetermined first amount ofthe obtained system oil providing tapped system oil and replenishing theremaining obtained system oil with a predetermined second amount offresher system oil, where tapping and/or replenishing is donecontinuously, near-continuously or intermittently.
 10. A methodaccording to claim 1, wherein the method further comprises the step oftapping a predetermined first amount of system oil from the engineproviding tapped system oil and replenishing remaining system oil with apredetermined second amount of fresher system oil, where tapping and/orreplenishing is done continuously, near-continuously or intermittently.11. A method according to claim 9, wherein the method further comprisesthe steps of: creating a cylinder oil on the basis of the tapped systemoil by determining at least one critical parameter of the tapped systemoil, determining at least one desired parameter of a cylinder oil andadjusting said at least one critical parameter of the tapped system oilaccordingly by blending the tapped system oil with at least one BNmodifying additive resulting in a created cylinder oil, and supplyingsaid created cylinder oil to cylinders or part of the cylinders of saidengine.
 12. A method according to claim 1, wherein said system oil isselected from the group of: a traditional system oil comprisingadditives for long-time performance or formulated with an additivetreat-rate providing long-time performance, and a consumable system oilwithout long-time performance additives or formulated with a reducedadditive treat-rate not providing long-time performance.
 13. A systemfor reducing fuel consumption in a two-stroke engine comprising: ablending unit for adding at least one friction modifier to at least apart of an obtained system oil, where the addition of the at least onefriction modifier reduces the friction coefficient of the obtainedsystem oil, resulting in a system oil with reduced friction and forsupplying said system oil with reduced friction to said at least oneengine.
 14. A system according to claim 13, wherein at least one of saidat least one friction modifier is an ash-less friction modifier.
 15. Asystem according to claim 13, wherein said at least one frictionmodifier is based on one or more selected from the group oftriglycerides (of animal and/or vegetable origin), such as rape seed,soy bean, and/or castor oil, fatty phosphates, fatty acid amides, fattyepoxides, borated fatty epoxides, fatty amines, polyol esters, boratedpolyol esters alkoxylated fatty amines, borated alkoxylated fattyamines, metal salts of fatty acids, sulfurized olefins, fattyimidazolines, or mixtures thereof
 16. A system according to claim 13,wherein the system is located offshore, on-site, on-board a vessel,and/or in a land based plant.
 17. A system according to claim 13,wherein the system further comprises: a controller for tapping apredetermined first amount of the obtained system oil providing tappedsystem oil and replenishing the remaining obtained system oil with apredetermined second amount of fresher system oil, where tapping and/orreplenishing is done continuously, near-continuously or intermittently.18. A system according to claim 13, wherein the system furthercomprises: a controller for tapping a predetermined first amount ofsystem oil from the engine providing tapped system oil and replenishingremaining system oil with a predetermined second amount of freshersystem oil, where tapping and/or replenishing is done continuously,near-continuously or intermittently.
 19. A system according to claim 17,wherein the system further comprises: a controller for creating acylinder oil on the basis of the tapped system oil by determining atleast one critical parameter of the tapped system oil, determining atleast one desired parameter of a cylinder oil and adjusting said atleast one critical parameters of the tapped system oil accordingly byblending the tapped system oil with at least one BN modifying additiveresulting in a created cylinder oil, and for supplying said createdcylinder oil to at cylinders or part of the cylinders of said engine.20. A system according to claim 13, wherein said system oil is selectedfrom the group of: a traditional system oil comprising additives forlong-time performance or formulated with an additive treat-rateproviding long-time performance, and a consumable system oil withoutlong-time performance additives or formulated with a reduced additivetreat-rate not providing long-time performance.
 21. A method accordingto claim 1, wherein the method further comprises a consumable system oilfor use in an engine, wherein the engine is connected with a controllerfor tapping a predetermined first amount of system oil from the engineproviding tapped system oil and for replenishing remaining system oilwith a predetermined second amount of fresher system oil, where tappingand/or replenishing is done continuously, near-continuously orintermittently.
 22. A method according to claim 21, wherein theconsumable system oil is formulated with reduced additive(s) treatrate(s).
 23. A method according to claim 21, wherein the system oil isformulated using additives/components and/or base oil(s) selected oneconomics rather than extended performance.
 24. A system according toclaim 13, wherein the system further comprises a consumable system oilfor use in an engine, wherein the engine is connected with a controllerfor tapping a predetermined first amount of system oil from the engineproviding tapped system oil and for replenishing remaining system oilwith a predetermined second amount of fresher system oil, where tappingand/or replenishing is done continuously, near-continuously orintermittently.
 25. A system according to claim 24, wherein theconsumable system oil is formulated with reduced additive(s) treatrate(s).
 26. A system according to claim 24, wherein the system oil isformulated using additives/components and/or base oil(s) selected oneconomics rather than extended performance.